Testing eyes



pril 15, 1941. A. AMES, JR., gil- AL TESTING EYES Filed Nov. 6, 1937 pril 15, 1941. A. AMES, JR., ETAL. 2,238,207

TESTING EYES Filed Nov. 6, 1937 11 Sheets-Sheet 2 PROJEC T0195 ADJUSTABLE 0N HEAD BAA/D5 April 15, 1941.

A. AMES, JR., Erm.

TESTING Ems Filed Nov. 6. 1937 11 Sheets-Sheet 3 April 15,1941- A. AMES, JR., ErAL 2,238,207

TESTING EYES Filed Nov. 6, 19357` l1 Sheets-Sheet 4 April l5, 1941- A. AMES, JR., E'r-AL 2,238,207

TESTING EYES Filed uw. e, 1957 11 sheets-sheet s April l5, 1941. A. AMES, JR., ETAL TESTING EYES 1l Sheets-Sheet G Filed Nov. 6', 1937 April 15, 194- A. AMES, JR., Erm. 2,238,207

TESTING EYES Filed Nov. 6, 1937 11 Sheets-Sheet B 11 Sheets-Sheet 9 ET AL i i /6 /4 /2 zo A. AMES, Jn.

'rz-swzm; Ems

Filed Nov. 6, 1937 JQJZ April 1s, 1941.

April l5, 1941. A.AME1S.JR., ETAL 2,238,207

TESTING' EYES Filed Nov. s. '1937 u sheets-sheet 1o Ewan-0 7'15. acgeler? aimee', 12

i em: Q' 1 April `l5, 1941.

A. AMES, JR., Er'AL 1-:Smm Ems Bled N9?. 6. 1957 11 Sheets-Sheet 11 lggfd SVMMETR/c IAsrA/METR/c @y 'Qfw Patented Apr. 15, 1941 TE STIN G EYE S Adelbert Ames, Jr., and Henry A.

N. H., assignors to Trustees of Imus, Hanover, Dartmouth College, Hanover, N. H., a corporation of New Hampshire Application November 6, 1937, Serial No. 173,110

32 Claims.

This invention deals with the testing of eyes and is particularly concerned with a method of examining binocular vision for all types of defects in a manner representing improvements as to simplicity, accuracy, versatility and adaptability, and with apparatus for carrying out this method.

Previous arrangements for example as described in Patent No. 2,095,235, of October 12, 1937, while suiiciently accurate and adaptable for most purposes, involve mechanical structures whose operation can not be easily supervised and controlled during operation; also, such instruments are rather expensive and not as universally adaptable to all kinds of ocular investigations and examinations as might be desired.

It is one of the principal objects of the present invention to provide an ocular test with the aid of test patterns optically projected in such a manner that they can be in a simple manner differentiated as to visibility to the respective eyes of a patient, and easily and accurately adjusted as to their spatial position regarding the patient, and the mutual position of test pattern components.

ln one aspect, our invention provides test bjects which can be simply and yet accurately changed, adjusted and regulated during the test by the patient as well as by the examiner, the latter being able constantly to supervise, to adjust, to modify andV to Irelocate test objects observed or `adjusted by the patient. In another aspect, the invention provides for the testing of all phenomena of binocular and monocular vision as refraction (including astigmatism), muscular conditions (phorias, tropias) aniseikonia (symmetric or asymmetric) and fusional response (foveal and peripheral), with or without maintaining binocular xation by using test patterns projected with light diierentiated for observation by the respective eyes, preferably by means of polarized light.

Further objects of the invention are improved tests for dioptric defects during binocular vision, of muscular defects, and especially of aniseikonia, which is defined as an anomaly of the binocular visual apparatus in which a difference or incongruity exists between the size or shape of the ocular images of the two eyes. The term ocular image" describes the iinal impression received in the higher brain centers through the vision of one eye. The effective magnitude and shape of this impression are determined not only by the properties of the dioptric image as formed on the retina, but also by the modifications imposed upon that image by the anatomical properties and physiological processes by which the optical image upon the retina becomes evident in the higher cortical centers.

Concerning defects of the last mentioned type., namely aniseikonia, the invention provides for the first time the possibility of comparing size and shape of ocular images either by maintaining or continuously changing the direction of the lines of vision of any one, or both eyes, and for investigating elementary portions 0f the visual eld for ocular image discrepancies. For that purpose, our invention permits the presentation to a pair of eyes of a test pattern only visible to one of the two eyes. of similar test patterns visible to both eyes, of similar patterns each only visible to one of the two eyes, and of dissimilar patterns each only visible to one of the two eyes; these patterns can be shifted at will over the entire field of vision and their relative position, size and shape adjusted in convenient and yet inherently accurate manner.

Still another aspect of our invention is an arrangement for locating in space the head of a patient without mechanically restraining it, providing the `possibility of determining the relative positions of testing apparatus, head, and eyes.

These and other objects, aspects and features of our invention will be apparent :from the following detailed description illustrating the genus' of the invention with reference to several concrete embodiments thereof. The description refers to drawings. in which:

Fig. l is a diagram illustrating the general principle of the invention; y

Fig. 2 is a diagram indicating the appearance of the fusion object shown in Fig. li; i*

Fig. 3 is a side elevation of one practical embodiment of the eye testing equipment .diagrammatically shown in Fig. ll;

Fig. 4 is a rear elevation of the equipment shown in Fig. 3;

Fig. 5 is an isometric detail of the head projector equipment diagrammatically shown in Fig. 1;

Fig. 6 is a top view of the projectors shown in Fig. 5;

Fig. 7 is a side elevation of another practical embodiment of the equipment shown in Fig. 1;

Fig. 8 is a top view of the equipment shown in Fig. 7;

Fig. 9 is a front view of the optical stand diagrammatically shown in Fig. 1;

Fig. 11 is a front elevation of the projector arrangement as shown in Fig. 3, with one side projector omitted:

Fig, 12 is a side elevation corresponding to Fig. 11;

Fig. 13 is a top view detail of the mirror support shown in Figs. 11 and 12;

Fig. 141s a side elevation of the hand projector indicated in Fig. 1;

Fig. 15 is a diagram of an interlaced mirror arrangement;

Fig. 16 is a side elevation of the projector battery indicated in Fig. 1;

Fig. 17 is a front elevation of the battery;

Fig. 18 is a detail of the battery dial board;

Fig. 19 is a detail of the battery adjustment device;

Fig. 20 is a front elevation of beam splitting device;

Fig. 21 is a section on lines 2 i-i of Fig. 20; Fig. 22 is a diagram illustrating a continuousadjustable depth fusion pattern;

Fig. 23 is an acuity test slide;

Figs. 24 to 26 are stereopsis test slides;

Fig. 27 is a pair of horopter slides;

Figs. 28 and 29 are phoria slides;

Figs. 30 to 34: are fusion pattern slides;

Fig. is a dioptric test slide;

Figs. 36 to 46 are aniseikonia test slides;

Fig. 47 is a diagram illustrating the appearance of an image projected with slides according to Fig. 24;

Fig. 4:8 is a similar diagram, illustrating the appearance of images projected with slides according to Fig. 34;

Fig. 49 is a diagrammatic representation of a horopter test;

Figs. 50 and 51 are diagrams explaining a declination test; and

Figs. 52 to 55 are diagrams explaining aniseikonia tests.

General method and arrangement- Referring with regard to various terms and fundamental concepts herein involved, especially concerning aniseikonia, to Patents Nos. 1,946,925; 1,933,578; Reissue No. 19,841; 2,063,015; and 2,095,235, the general aspect of the ocular test according to our invention will first be explained by referring to Fig. 1, without describing in detail any of the testing operations or devices.

In Fig. 1, the location in space of eyes R and L of a person is, for example, determined by means of projectors PV and PH fastened to the patlents head and directing light rays towards graduated screens TV and TH, respectively. In front of the left and right eye are arranged light polarizing screens NL and NR, respectively, for example of the type described in Patent No. 2,011,- 553. Th' axes of polarization of these screens are inclined at an angle of 90, so that light polarized in the axis of one sheet will be substantially absorbed by the other sheet. Herein, polarizing elements effective in the same manner as screen NL, and light polarized by such elements will be indicated by letter l, elements and light similarly related to screen NR by letter r, l, r will signify two identical patterns projected in register with l and 1- light, respectively, and elements and light not having any polarization characteristic will also be denoted by l, 1', the physiological effect being in both instances essentially similar.

Provisions are made to arrange before each eye optical elements, as test lenses or prisms; in Fig. 1, such provisions are indicated by trial lens s. Masks excluding extraneous influences inducing binocular depth perception may be provided. for example by hanging on screens NL and NR sheets (indicated at! for screen NR) with round and square openings, respectively. In order to permit convenient observation of the'eye positions by the clinician, an inclined mirror (or mirrors; indicated at m for the left eye only) may be arranged which reilects upwardly images of the eyes.

In order to carry out catoptric observations, a telescope with light source may be arranged for rotatory adjustment about the centers of rotation of the respective eyes. Fig. 1 indicates, by way of example, a mirror OK for reflecting light from catoptric telescope K into the right eye and from the eye back into the telescope; both mirror and telescope are mounted on a carrier rotating about center of rotation CR.

In order to permit certain investigations, for example direct dioptric measurements, a haploscopic device may be provided for either eye. Such an arrangement is indicated in Fig. 1 by reflector OH (preferably transparent) and dioptric test target d, arranged for rotation about the horizontal and vertical axes of rotation of the eye. An instrument similar to that described in Patent No. 2,095,235 may be adapted for this purpose as Well as for mounting the catoptric device.

Arranged as closely as possible to the eyes are light projecting means, Fig. 1 showing by way of example one central projector PC and two side projectors PL and PR, respectively. The projectors have light sources g, projector lens systems p and provisions for inserting slides. These may be single slides, as indicated at GL and GR., or slide strips, as indicated at PG for the center projector, permitting quick and convenient change of slides. As indicated, the slides are preferably rotatable about the optical axes of the projectors.

The projectors are further equipped with polarizing screens, for example ML, MC and MR; as indicated at MC, a double screen with elements having axes crossed at may be provided for rapid change from a l screen to a r screen or, as indicated at MR, the polarizing screens may be arranged for rotation about the projector axes, for similar purposes. The polarizing screens should, of course, be arranged for easy removal.

The projectors may be combined with optical devices permitting controllable modification of the projected images; at i of Fig. l is indicated a holder arrangement for test lenses, and at :i an optical system, for example of the type permitting gradual change of the size of the projected image While keeping it in focus.

As indicated in Fig. 1, each projector is adjustable, if desired universally; scales or indicators for determining the amounts of adjustment are provided.

It is often desirable to adjust in convenient manner and more or less independently the re1- ative location of the elements of a single test pattern, While being able also to adjust or relocate the entire pattern. For that purpose, a so-called battery projector B may be used, having for example four projector components BI, B2, B3, B4, each provided (in similar manner as for example projector PC) with light source, slide, projector lens system and polarizing screen, and independently movable as indicated, whereas the battery as a whole is universally adjustable relatively to the eyes.

'projectors may likewise be third chart or The arrangement may further include one `or more projectors for manual operation by patient or clinician, indicated at PM of Fig. 1. Buch equipped with slides and polarizing screens.

Arranged in iront of patient and projectors is a screen S covered with material reflecting polarized light without substantially ailecting the polarization, as for example a coating of aluminum. 'Ihe screen S may be fixed to the floor or other support coordinating patient, eye equipnient and projector equipment, or it may be adjustable as to distance from and inclination to the eyes, as indicated at A of Fig. 1 by a movable platform to which screen S is hinged.

For the overall illumination of the screen an intensity should be selected which permits perception of projected images which are lighter as Well as darker than the screen surface itself.

For testing eyes according to our invention, the patients head is, for example, located, as above mentioned, by attaching to his head projectors Pi-l and PV thereby indicating the head position on screens TH and TV. By using proper slides and polarizing screens in the projectors and corresponding screens before the eyes, the patient is now presented with test patterns, for example the following basic ones for dioptric, muscular and aniseikonia tests, as follows:

its indicated at IS and 1P of Fig. 1,` slide G is adjusted to ci.v .e projection of a dioptric test pattern for example in the shape of three customary Snellen charts, which, however, are dii'- ierentiated by means of polarization. For example, the two outer charts of slide element IP may be covered with l and r polarizing material, respectively, whereas the center chart of the slide is not screened. If the patients eyes are screened with l and r polarizing material, as indicated at NL and NR, he will see the projected l, r image of the center chart with both eyes, the i jme with the left eye. and the r image with the right eye. Similar results could be obtained by projecting unscreened single charts with side projectors PL and PL equipped with l and r polarizing screens, respectively, and projecting a fusion pattern with center prolector PC using unpolarized light. It will be evident that binocular fixation is secured in this manner, whereas each eye can be separately (monocularly) tested for dioptric defects. The dioptric defect can be determined by correcting the eyes with test lenses at s, or the test pattern sise may be changed by appropriate means, for example optical system j.

llor phoria tests, a graduated pattern II may lbe projected on the screen as image IIS, through l material and therefore only visible to the left eye. il light point IIU is projected, for example `with r polarized light, by means of hand projector PM. The clinician sees the entire test pattern IIS and IIU with both eyes, whereas the patient sees IIS with the left, and IIU with the right eye only. It will be evident that muscular defects can be detectedand measured by comparing the actual location of IIS and IIU when the patient adjusts projector PM causing IIU to appear to him at ing the relative location oi' IIS and IIU as appearing to the patient when the operator directs IIU to fall on o. By inserting optical prism means at s before the patients eyes, prismatic corrections can be evaluated.

iior investigating aniseikonia, a pattern IIIS comprising -a fusion object F and companion obpear three dimensional lo Dl may be projected with l rectly, test object d of mirror OK into jectors, as indicated at be arranged at adlstance center o of IIS, or by compar-V indicated at A of Fig.

projector GL. The circle of F will then be visible to both eyes,

whereas each point is only visible to one eye.

Hence, the fixation object will apas indicated in Fig. 2. provided, of course, that the patient is at all able to fuse. This stereoscopic type of fusion object is especially adapted to induce and to hold fusion. As a comparison pattern, four lines DI, DI, DI, light through the center projector PC, as indicated at IIIP, combined with arrow lines, indicated at D2, D4, DI, DI, and projected with r light, for example by means of battery B. If the clinician align; for

2o his binocular vision. the z and r unes as shown Et IIIS, the patient will observe apparent deviations of the lines if he has aniseikonia. By adjusting `the individual projectorsl of the battery, or by optically changing for example (with j in the 25 case oi overall aniseikonia) the dimensions of the l pattern, or by appropriately adjusting or setting trial lenses s, the aniseikonic defect can be measured. l;

If it is desired to measure dioptric defects dican be moved on the arms of haploscope H; by swinging the haploscope arms, muscular defects can be investigated.

By projecting the reiiections of a light point from surfaces of the catoptric telescope K by way an eye and observing the reflected light points through the telescope, conditions of the optical surfaces of the eye can be investigated in well known manner.

peripheral, `a test object IVS may, for example, be used, comprising two dissimilar patterns Fi and F2, respectively. One pattern is presented to the left eye only and the other to the right eye only, for example by means of the side pro- IVP and IVP' of Fig. l. When fusion is normal, Fl will appear to move relatively to F2 with relative movements of the respective eyes. The amount of movement can be measured through the displacement of Fi and F2 reported by the patient, or adjustment necessary to center Fi relatively to F2. It is very important that the test pattern elemens of an object of this type can be moved together over the entire field, permitting examination of foveal as well as peripheral fusion. and testing of variations in fusional ferent parts of the field, by moving the fusion objects.

For testing long distance vision, screen S will from the eyes of prei'- erably not less than 6 m., with the horizontal line of vision normal to the screen. For testing vision at the second principal position, that is as when reading, a screen will be placed at about 40 cm.

correspondingly 5 from the eyes and normal to a line of vision directed downwardly at an inclination of about 20 to the horizontal. It is quite feasible to employ one and the same screen for both positions, by means of the above-mentioned provisions, as 1. Instead, two separate screens may be used. It will now be evident that the,- size of the images produced on the screen can be readily controlled, so that any visual s angle, coordinated to any type of test at any distance, can be obtained.

For testing fusipnal response, foveal as well as* response in diiby the lantern Although polarized light carrying out our invention, other possibilities of light diierentiation could be employed, for example the use of colored light in place of polarized light. Instead of using light polarized in different planes, and screens before the eyes which correspondingly absorb the differently polarized light, colored light and correspondingly colored filters before the eyes could be used. For example, yellow and green light with filters only transmitting yellow or green, respectively, may be employed, together with white light for fusion patterns to be visible to both eyes, instead of the l elements, the r elements and the l, r elements, respectively. The yellow and green spectral ranges are preferable to the red and green ranges, for example, because chromatic abberation in the eye regarding green and yellow is practically negligible.

It will now be apparent that our new testing method makes possible, with simple means, an extremely comprehensive and accurate, and yet simple test whereby all possible ocular defects can be investigated as to their correlated as well as individual characteristics. More detailed descriptions of the various phases of representative tests and of the apparatus preferably used for carrying out these tests will now be presented by way of example, for the purpose of promoting a better undestanding of the invention.

Ocular equipment-Referring to Figs. 1 to 10,

is preferably used for vthose aspects of the invention will now be described which relate particularly to locating and observing the eyes and to optically affecting the light reaching them.

As mentioned above, it was found practical, and in many instances preferable, to supervise the spatial relation of eyes, head and test objects optically rather than by means of' mechanical devices.

As shown in Figs. 1, 3, and 5, the patient is provided with a head gear, for example consisting of two bands i and 2, carrying two small projectors PH and PV by suitable means, for example ball and socket joints 3 and ll, respectively, the projectors being supplied with current through cord 3. These projectors are so arranged that their optical axes pass as nearly as possible through the center of rotation of the head, or the cyclopean eye, as indicated in Fig. 6. The patient is placed between screens TV and TH, which are provided with two-dimensional scales, for example of the type usually carried by the so-called tangent screens. The head of the patient may be entirely free, or he may be assisted, for example, by a portable chin rest li supported on stand i@ (Fig. 3). The two projectors trace on their respective screens with light points the vertical and horizontal axes through the patients head; in this manner the clinician is enabled continuously and reproducibly to supervise the head position and exactly to trace head movements. In primary position, the narrow light beams coming from projectors PV and PH are falling at the centers of screens TV and TH, respectively. Other positions of the head can be obtained either by maintaining the light spots at other points of the screen or by moving projectors PH and PV relatively to the head gear so that the light spots fall on the screen centers for other than primary head positions. It is often important to control the position of both head and eyes relatively to the test object, since the ability to fuse depends to some extent on the relative positions of eyes and head which, therefore, must it is understood that be taken into account and reproducibly established. The eyes being located by looking at a test object, and the head by means of the above double projector device, these conditions are fulfilled. Also, the head can be moved to any measured degree by retaining eye fixation, or the eyes can be moved by moving a fixation object, while the head is maintained xed.

Together with the above described head positioning device is preferably used a stand (Figs. l, 3, 9, and 10) resting on, or screwed to the door and carrying the eye equipment previously described. A block 2i with extension rod 22 is fastened to stand 20 for horizontal and vertical adjustment by means of screws 23 and 24. Instead of having a separate support I0 as shown in Fig. 3, chin rest Il may be fastened to stand 2U, as shown in Fig. 10. Fastened to block 2i are lens holders 25 for trial lenses s, observation mirror m, polarizing screens NL, NR, and diaphragms i.

In the embodiment shown in Figs. 7 and 8, trial lens holders and polarizing screens are fastened to a haploscopic instrument I-I in a manner which will be evident, for example from Patent No. 2,095,235. From this patent it will also be understood that the continuously adjustable size lens system described in copending application Serial No. 713,701 can be mounted either on stand 2c or on haploscope H. Figs. 6 and 8 illustrate further the possibility of using a head support with chin and forehead rests instead of the projector device shown in Fig. 3. These figures also show the manner in which a dioptric test target d and a catoptric device K can be mounted on the arms of a haploscopic instrument, for purposes of combining corresponding tests with the tests by means of projected differentiated test objects.

Projector equipment-Referring to Figs. 1, 3, 4, and l1 to 19, the projector equipment of preferred embodiments of the invention will now be described. Fig. 1 shows a center projector PC, and two side projectors PL and PR at a certain distance from the center projector. This arrangement, although for many purposes sufficiently accurate, involves certain inaccuracies due to the fact that the different inclinations between screen, and optical axis of the projectors and visual axis, respectively, might cause undesirable dimensional discrepancies between the images of test pattern elements projected from different lante; ns. The arrangement shown in Figs. 11 to 13 is more satisfactory in this respect. This arrangement employs mirrors which bring the origins of the side projector light beams fairly close together and permits easy handling of the projectors which can be arranged at convenient distances from each other.

A table 3i, if desired fastened to the oor or other base 32, supports a mirror pedestal 33, two side projector bases 34 (only one side projector is shown in Fig. 11, the other being symmetrically arranged), and a center projector pedestal 36 (Fig. 12). Each side projector base supports a baseboard 31 with standard 38 and capstan screw 39. Hinged to standard 38 is frame 4| with projector CR and optics support 42. The projector may be of the standard magic lantern type, but the slide carrier 42 should 4be of the rotary type and provided with scale and index 43. Support 42 should permit easy interchange of polarizing screens and optical systems indicated at i and y of Fig. 1. Scales and pointers 44 permit reading of the inclination of the projectors.

Top 5I of center projector pedestal 36 (Fig. 12)

carries a baseboard l2 pivotally fastened at Il. A screw 54 extending through an arcuate slot of top 43| permits rotary adjustment of board l2 and ilxation of the latter to top 5|. A pivot bracket 53 of board 52 supports projector PC, and a screw arrangement 53 permits adjustment of the projector about pivot 51. .Scale and index means I3, 59 may be used for determining the rotatory projector adjustment in vertical and horizontal planes, respectively. Similar to the side lanterns PR and PL, center projector PC has a slide support 6| and an optics support 62, both being preferably rotatable about the projector axis.

Mirror pedestal 33 supports a mirror baseboard 1| (Fig. 13) carrying two mirror holders 12 and 13 pivoted to the board at 14 and 15. The baseboard itself is connected to pedestal 33 .by a pivot pin 16. Scales and pointers 1.1 and 18, respectively. permit reading of the position of the mirrors relatively to baseboard 1|, and by tightening screws 3| and 82, the mirrors can be xed relatively to the board. Scale and index 33 relate board 1| to pedestal 33. L

Mirrors 3E and 81 are fastened in vertical position to holders 12 and 13, respectively, and it will now be evident that they can be adjusted separately or together, permitting the separate relocation of each side projector image and also of both images together.

The freely adjustable hand projector .indicated at PM oi Fig. 1 may be of any suitable type; a preferred form is shown in Fig. 14. In this gure, 9| is a stand which may have a base, as shown, or may be screwed to the floor or other support. The projector PM proper is equipped with slide magazine 92, swivels 93 and 94 for horizontal and vertical movement, respectively, and receptacle 95 for polarizing screens. A handie 96 permits convenient adjustment by the patient or the clinician. Several of these projectors may be required, as indicated in Fig. 2. They may be used for projecting test patterns, or for example as pointers permitting patient or examiner to indicate details of the test pattern on the screen.

Instead of using two mirrors as shown in Figs.

l1 and 12, the optical axes of the side projectors maybe brought to coincidence by employing a divided projector lens `system or an interlaced redactor or prism system. The latter possibility, providing a substantially idea1 side projector ar rangement, is indicated in Fig. 15, where 91 and d are the reecting surfaces and 99 is the common optical axis. With an arrangement of this time; the entire image adjustment would preferably be taken care of by means of the projectors themselves.

llt will be understood that each projector as well as the mirror system could be made universally adjustable, and that the adjusting movements of any group of projector elements could be coupled. Also, the beams could be moved by means of adjustable mirrors only, in which case the projectors could be fixed to a support in any convenient position. It will further be evident that, as indicated at 49 of projector CR (Fig.

`l'l), each projector may be equipped with special optics, as for example trial elements as sizel lenses or prisms, systems changing the image magnincation without aiiecting vergence power, or changing dioptric power Without alien-ting the magnification. Remote controls of such systems, for operation by patient or clinician, can be --easily arranged, as will be understood without detailed eral portions explanation. As already mentioned. the `slides are preferably rotatable. '.ljhe` Ipolarizing screens and their holders should be'arranged for easy re" moval and re-insertion of `thiij-latten atter'havmg been turned 90. A switchen arneostat for each projector lamp are preferablvlprovided at easily accessible points, 'sa'that the projec tors can beconvenlentlybrought into, and eliminated from operation,` and the light intensities of the images on the screen properly correlated.

Sometimes it becomes desirable to introduce an intermittent stimul This is accomplished by using a dicker arrangement including, for example, a shutter (Figs. 11 and 12) driven by 'motor |02 through a suitable transmission |03. A drive permitting speed variations within a range of 100 to 6000 R. P. M. of the shutter dish. was found suitable. As shown in Fig. 11, the circular disk has a window |04 covering one haii' of the diskarea; a counterwelght |05 is preferably provided to balance the disk. The fact that the peripheral portions of the retinaare more sensitive to the flicker effect than the center, can be taken care of by projecting the periphside lanterns having the flicker equipment,

whereas the central portion is produced with the third projector, not affected In order to show the adaptability of the new ocular test, an alternative arrangement will now be described, with reference especially to Figs. 7 and 8 and 16 to 19. As indicated in Figs. 7 and 8, a haploscopic device H similar to that shown in the above-mentioned Patent No. 2,095,235 is Iastened to table As previously mentioned, the head rest I oi.' this device is used and likewise its trial lens equipment and its light deviating mirrors OI-I or OK (Fig. 1) A single center projector PH is fastened to table by meansl of clamp H2 having vertical pivot ||3 and horizontal pivot ||4 for purposes of moving the projected image relatively to the screen means.

The battery B, shortly described with reference t0 Fig. 1. lends itself Very Well for use in this test for example, instead of center projector PC. `In combination with a set up as shown in Fig. 8, the

of a given test pattern with the by the flicker disk.

battery is preferably placed on an extension table |21.

Referring now especially to Figs. 16 to 19, a projector battery will now be described. Table |2| supports a plate |23 which can slide on the table around a pivot and xation screw |24. Plate |23 has a base yoke |25 to which, at |25, is hinged battery base |3|. By means o1' a capstan screw |21, base |3| can be swung around pivot |26. Scales (not shown) for measuring the adjustments around |24 and |26 may be provided,

Base |3| for example a casting, has a dial panel |32 and a projector tube frame 433. Four dial control shafts |34 (Fig. 16) are journaled in panel |32, carrying dial knobs |35 with dial scales |36 (Fig. 17) on the outside, and cams |31 on the inside. Tube frame |33 supports four U-shaped projector element carriers |33 (Fig. 17), provisions for initial adjustment being made for example by means of leaf springs |39 and screws |40. Pivotally fastened to carriers |38 are the front ends of projector elements BI, B2, B3, B4, (compare also Fig. 1), whose back ends are correlated. with cams |31 and knobs |35, for example by mean'of follower arms |4|, brackets |42, adjustment screws |43 and springs |44 held within panel |32 by screws |45. It willv now be evident that the battery as a whole can be adjusted in order to coordinate the entire projected pattern with the screen, and that each individual pattern element as projected by the individual projector elements can be separately adjusted, and the adjustment read by means of dial scales |38.

As indicated in Fig 16, the projector lamps are supplied with current through cords |41; slides |40 can be exchanged, and polarizing means NB adjusted by suitable means.

As will be apparent from the description of test methods given hereinafter, as many as six or more projectors may be used, whereas it will sometimes be possible to make satisfactory tests with a single lantern, or two lanterns, and a spectacle frame. Battery Bdnay be combined with such a simple set up, or, as indicated in Fig. 1, with the more elaborate arrangement shown in Figs. 3 and 4. It will now be evident that the new test is adaptable to the most varied conditions and requirements and does not require any precisely made and adjusted mechanical equipment, since the correlation of the test patterns can be supervised and changed simply by observing the screen. Even the simple adjustment provisions herein shown by way of example are comparatively elaborate and, although desirable, maybe,

replaced by simpler arrangements as mounting boards and clamps.

For the relative adjustment of l and r images, respectively (for example for purposes of the test indicated at 1V of Fig. 1), a projector may be provided with a continuously adjustable beam splitting device. Figs, and 21 illustrate an embodiment of such a device. In these figures, |80 indicates the objective lens system of a projector |8|. Fastened to the lens mounting at |82 is a system |90 of two prisms |83 and |84 relatively rotatable by means of knob |85. As well known in the art, the prism power of such a system varies with the relative position of the two component prisms and can be read by means of a scale |86. As indicated in Fig. 20, the aperture ring not covered by system |90 is provided for example with r polarizing material pr, and system |90 itself with lpolarizing material pl. If the prism power is zero, the l and r images of the projector slide will coincide; upon increasing the prism power by turning knob |85, these images will gradually move apart. It will be understood without detailed explanation that arrangements for rotating the polarizing screens, or both, images, or each image separately can be provided, and that other light splitting devices could be suitably adapted.

Screen equipment- As mentioned with reference to Fig. 1, one type of screen now preferably used consists of a plaster base having an aluminum coating; 'a cloth base is also suitable. We found that such a screen does not substantially interfere with the polarization characteristics of light reflected therefrom. An ideal set up would be one with a screen spherically curved about the cyclopean eye of the patient, with the projector optics also centered at that point. By comparatively complicated optical arrangements this ideal condition could be fulfilled. A cylindrical screen curved about an axis through the cyclopean center CC (Fig. 1) .may sometimes be desirable, but for most practical purposes the equipment above described is fully satisfactory in combination with a flat screen substantially normal to the visual axis of the patient. In order to fulfill the last mentioned condition, the screen may be made adjustable as shown in Figs. 3 and 4. In these figures, |5| are tracks supporting by means of rolls |52 a screen platform |53 to which is pivoted at |54 a yoke |55 for screen S which swings in |55 on journals |56. Scale means |51 permit reproducible adjustment, and fixation screws (not shown) may be provided in suitable manner.

A screen of this type may be used 'for far as well as near vision, and for any intermediate position that may be desirable. By rotating it about its vertical axis, the relative size of images projected onto opposite sides of the screen may be changed and measurably adjusted, as indicated at S of Fig. 3.

Fig. 'l shows an embodiment with two screensi" distant vision screen Sd is fastened to fioor'or other support 32, whereas a small screen Sn is xed to table l||, for near vision (reading) tests. Projector PH may be used for. either screen, but in this embodiment we prefer a different type of near vision screen, a preferred embodiment of which will now be described.

As shown in Figs. 'l and 8, table supports a small screen plate Sn, preferably of glass, being provided with a thin layer of aluminum (for example applied by sputtering), which layer partly reflects and partly transmits light, a device well known in the optical art, for example for light dividing reectors. A small projector PR likewise fastened to table and preferably arranged for universal adjustment, is used for projecting test images onto the back side of screen Sn. We found that semi-aluminized screens of this type transmit as well as reflect light without appreciably changing its polarization characteristics as far as they are used for present purposes.

Similar to the above described arrangement, a semi-transparent screen may be used with a rear projector, or projectors, for example, for distant vision tests, with a set up according to Fig. 3. This set up may be employed with the battery B not in front of screen S but in the rear of a similar, but semi-transparent screen SS, as indicated in Fig. 4.

A semi-transparent screen may also be used for producing depth fusion patterns with an arrangement according to Fig. 22. Two lamps 22| and 222 project light beams through a circular opening 223 of mask 224 onto screen SS, the41 light being I and r polarized, respectively, as indicated. The eyes being provided with l and 1 polarizingscreens NR and NL observe only the respective polarized light spots 225, 226 on the screen, the resulting stereoscopic effect causing a single dot to appear beyond or in front of the screen. By gradually changing the distance of lamps 22|, 222, the distance of light spots 225, 226 can be similarly changed, thereby correspondingly modifying the apparent distance of the binocularly fused spot from the screen. This device is especially suited for investigating depth perception latitude, as it permits a gradual approach to the point where fusion breaks.

As mentioned above, the semi-transparent screen shown in Figs. 7 and 8 may be used with lantern PH (Fig, 7) projecting test patterns.l upon its front surface, since the semi-transparent screen, while obscuring to the eyes of the patient objects therebehind, makes visiblelight projected thereon from either side. As shown in Fig. '7, a hinged cover 23| may be added to screen Sn, for example a plain aluminum sheet, if it is desired to use an opaque screen instead.

It will now be'evident that the screens for rasend? reiiecting or transmitting (or both) polarized lights can be made opaque for receiving light from one side only, r semi-transparent for receiving light from either one or both sides.

Slide equipment- For projecting test patterns on the test .screen various types of slides carrying such patterns in the form of sections of ditlerent transparency, or analogous devices can be used, a selection of which will now be generally discussed, a more. detailed explanation of their function being reserved for a description of various representative applications of the new test method.

It will now be evident that the invention makes use of unpolarized light and of light polarized in different planes, herein referred to as l, r, l and r polarized light, respectively. Each lantern, through appropriateV slides, may be used to made with regard to the actual transparency difterences of the various slide sections. but rather separate polarizers, or these portions may themproject light of any one particular type, either polarized or unpolarized. i In that case, a polarizing screen is preferably `inserted in the light beam at any convenient point, for example by covering the slide itself with a polarizing sheet or by using a screen as at MC, MR or ML of Fig. 1. By arranging for interchangeable screens (as at MC of Fig. 1) or for rotation of the screens (MR) the polarization plane can be changed. Unpolarized patterns l, r can, of

` course, be obtained by removing a screen; but

it is also feasible to project superimposed images of similar patterns with l and r polarized light, respectively, which l, r patterns will then be visible to both eyes although, and this is very important, they can be easily separated by adjusting their individual sources. i

lit is further possible to project polarized as well as unpolarized light with a single projector, by covering portions ci a slide with appropriately orientated polarizing material.

There are several possibilities of relatively adjusting the images on a screen. With slides lined in separate projectors, the images may be movedby moving the projectors relatively to each other; slides with mechanically adjustable portions (for example similar to the targets shown in Patent No, 1,944,871) may be used; or the light beams of'the projector may be optically adjusted as by adjustable projector lens systems (change of focus), lens systems (image size or shape changes), or prisms (asymmetric displacements). Needless to say, scale means can be applied to all adjustment movements; in many cases it will be preferable to incorporate scales as part of the test pattern, which permits direct quantitative detection of the defect in question, especially of aniseikonia or muscular defects (phorias and tropias).

A number of representative slide systems Will now be described by way of example, with reference to Figs. 23 to 54.

Fig. 23 shows an acuity chart, already shortly described with reference to IS of Fig. 1. In this slide, the center part 250 transmits unpolarized light, whereas the side parts 25| and 25|- transmit l and 'r polarized light, respectively. Instead, three slides similar to center portion 250 can be used in three different projectors, the lanterns projecting the two side images being used with l and r polarizing screens, respectively, and adjusted to produce on the screen a combined image resembling Fig. 26.

In this connection it should be noted that either the slide pattern or the background may be transparent, in accordance with the test conditions in every instance; the-'drawings are not selves be covered with polarizing material, as for example above described with reference to Fig. 23.

Fig. 24 depicts a pair of stereopsis slides for use in two respective (for example side) projectors, one for l and the other for r light. Rings 253, 254, 255L, 255R and points 255L, 256B will appear as shown in Fig. 47.

Fig. 25 is a pair of slides, for two Z and r, respectively, projectors, representing the well known Keystone pattern consisting of geometrical elements 258, adapted for purposes of the present invention, or on a transparent ground 259 which is l or r polarized for the two slides, respectively.

Fig. 26 is a pair of slides forming a stereoscopic tipping iield pattern; the slides have identical irregular design 268 on l or 1', respectively, polarized ground 269; the images are somewhat displaced on the screen.

Fig. 27 is a pair of identical slides to be used with l and r, respectively, projectors, each having a series of transparent verticals 21| on ground 212; these slides are used for a horopter test.

Figs. 28 and 29 are phoria charts, each to be used in a separate l or r projector. Fig. 28 represents a grid 28| divided in arc degrees, on a ground 282, and Fig. 29 a two-dimensional tangent scale 2Bl on ground 292.

Figs. 30 to 34 are fusion patterns; Fig. 30 represents a pair of identical slides for projecting a polarized fusion pattern, that is a pattern composed of two identical, superimposed l and r, respectively, images produced for example by squares 30| on ground 332. Fig. 3l is a small light spot, for use in a hand projector PM, for example. 3|| being a transparent dot on opaque ground 3|2. Figs. 32 and 33 are single slides for l similar individual use. and represent an arrow 32| and a line 33|, on ground 322 spectively. Fig. 34 is a single slide; portion 26| is opaque, transparent dots 262 are covered with l polarizing material, and dots 263 with r polarizing material.

Fig. 35 represents a pair of dioptric chart slides for measuring astigmatism, with star patterns 35| on ground 352; they are preferably used in rotatable holders with individual l and r projectors, combined with a fusion image projected by a third lantern. M

Figs. 36 to 40 represent pairs of slides for aniseikonia testa, one slide in each instance to be used with i light, and the other with r light.

and 332, re-

Figs. 41 to 46 show single slides also for anisei-g konia investigations, the elements of the comparison pattern being in this instance differentiated by applying polarizing material directly to the slides. The slides, shown in Figs. 41, 42, 44, 45 and 46, require only a single projector for carrying out an aniseikonia test, whereas the slide according to Fig. 43 requires an additional lantern, or lanterns, for projecting a fusion pattern. In each instance, 36| and 362 are preferably transparent designs for the left and right eye, respectively, on an opaque ground 363. the monocularly observed portions being again marked l and r, respectively, and the Ilxation objects being marked Ir as'abcve described. Numeral 364 denotes the fixation pattern,

. Operation.--Referring also to the preliminary explanation of. the new test method in general, presented above lwhen describing Fig. 1, several specific instances of testing operations carried out according to the invention will now be described by way of example.

Visual acuity may be tested as described above with reference to IS of Fig. 1, by projecting three Snellcn charts, one as fusion object with l1' or l, r light, one with l light, and one with r light, for example by means oi` slide Fig. 23. Instead, only one chart may be projected with polarized light for monocular observation, and the eye under test changed by -rotating the polarization screen 90. Other possibilities are to cover one-half of a single Snellen chart with polarizing material and use it with a single projector, or to project a separate fusion object with unpolarized light and combine it with the polarized image of a dioptrlc test chart.

For testing astigmatism, a pair ofV slides, or a single slide, according to Fig. projected with l and r light, respectively, may be used, together with a suitable fusion object, in similar manner as above described. The sharpness of `the radii of the respective images will indicate the astigmatic meridians, while binocular vision is maintained. After, by conventional methods, one of the astigmatic foci was conjugated to screen,

the amount of astigmatism can be determined with charts as above described with reference to Fig. 23. g

A representative phoria or tropia test has been described above with reference to IIS of Fig, 1. Slides which may be used for such tests are shown in Figs. 28 and 29 and in Fig. 31. A slide according to Fig.'29 or 33, respectively, is projected with l or r light, and a slide according to Fig. 31 with r or l light, respectively.

Slide, Fig. 28, supplies a screen image graduated in angular degrees, whereas Fig. 29 illustrates a slide for projecting a screen with tangent scale having the well known advantages of such screens.

By projecting a slide according to Fig. 28 with 1 light and a 'similar slide with r light (a simple cross pattern may be used instead), cyclophoria and declination defects may be investigated.

A testtpattern combined of similar l and r images and seen by the examiner as a single cross as lindicated in Fig. 50, will appear to a patient having a rotational incongruity as illustrated in Fig. 51. The displacement of the centers as well as the angular deviation can be read by the patient; or, the apparent pattern can be made to conform to Fig. 58 by suitable optical means (compare copending application Serial No. 160,- '784, filed August 25, 1937), or by,relatively rotating the slides and shifting theprojectors. The amount of the defect can be determined from this adjustment, and the effect of corrective lens means accordingly checked.

Tests of this type often indicate' that the defect depends a good deal upon the relative position of eyes and head. In such instances, the determination of the head position by means of a device as shown in Figs. 1, 5 and 6 is indicated.

A basic aniseikonia test has been presented means of test lens systems before the eyes, or by both these provisions. For patients having squint, the images can center portions fuse.

The slide pair according to Fig. 40 provides (like that according to Fig. 39) a depth '(stereo) fusion object; it is used with a third lantern projecting an arrow (compare Fig. 32) seen by that eye only which also sees the image projected by the right hand slide of Fig. 40. The third lantern is preferably operated by the patient who brings his arrow successively into apparent alignment with the four arrows visible to the other eye. The scale lines of these latter arrows permit the examiner to read the size differences directly from the projection screen.

Single slides, Figs. 41, 42 and 43 are provided with polarizing material in such a manner that with reference to III of Fig. 1. Instead of using A test pattern III of Fig. 1, slides according to Figs 36 to 39 can be used with only two lanterns, in a manner which will now be readily understood. The relative size Yof the l and r patterns can, for example, be adjusted by using a size. changing optical system with one or both lanterns, or by -ment to fuse.

elements, t, 3, 5, 1 are seen with one eye and elements, 2, 4, 6, 8 with the other eye. Slide, Fig. 41, has a depth fusion object with the dots visible to respective eyes; slide, Fig. 42, has a simple non-polarized fusion object, and slide, Fi'g.43, is used with a separate fusion object prof jected from another lantern, or, preferably, with a screen having a black dot painted thereon. Slide, Fig. 42, has angles and lines, respectively, instead of arrows as in Fig. 41, for the purpose of avoiding confusion which sometimes occurs with slides of the pattern according to Fig. 41, when the common fusion object does not hold fusion-exactly, or when there is a slight phoria. A depth fusion pattern could be -used with this slide, similar as in Fig. 41.

The slide according to Fig. 44 has arrows or similar elements, with'scale lines, seenby one eye, and a fusion object seen by both eyes; the spaces opposite the arrows receive mechanically adjustable elements visible to the other eye'. Otherwise, this test is similar to that described with reference to Fig. 40.

The single slides according have a stereo fusion object as indicated, a scale and horizontal line visible to one eye, and a hori'- zontal line visible to the other eye. These slides' are used for measuring vertical and horizontal size difference, respectively, without eye movement, as will now be explained.

The tests now to be described are selectedv as examples of tests which could hardly be vcarried out according to previously known technique. In previous tests, there may take place a change of the direction of gaze; in the tests now to be described, the direction of gaze is constant. This has the advantage of eliminating any possibility of influence of muscular anomalies that might be associated with a change of the direction of gaze.

Fig. 52, as well as Figures 53 to 55, (in which a simple fusion pattern is indicated in order to simplify the drawings) show in the left-hand column the test pattern as it actually appears on the screen and, in this form, is visible to the examiner, whereas the right-hand columns show the respective pattern as it appears to the patient.

Two arrows, for example, are projected by means of slides Fig. 32, with l and r light, respectively, from two separate projectors. The patient, equipped with corresponding l and r polarizing screens, will see the arrows aligned as indicated at A of Fig. 52, because there is no induce- This appearance is quite independent of the presence of an aniseikonic defect. A fusion object is now introduced into the be so adjusted that the' to Figs. 45 and 461V Y oi. course, be proved by providing an eye of the periphery oi the field oi.' vision. for example by projecting aslide, Fig. 45 dr`46, with unpolarized light. Ii' the patient has-an ocular image diilerence in the verticalmeridian he will bserve the arrows to separate while he continues to iixate them in the center; of the held o! vision;

compare B of Fig. 52. It is herein presumed that lthe ocular image o1' the right eye is larger than that of the left eye.

the further the greater the distance of the i'usion 10 The arrows will separate object from the arrows at the center. and the greater the ocular image incongruity, as will be clearwhen considering' that the distance between the arrows represents the difference oi' the distances of two corresponding pairs of ocular imagepoints, which difference increases with distances increasing due either to outward movement oi' the fusion object or increase of the ocular image difference. The latter eil'ect can,

` means of a slide according to Fig. 44, the examiner can bring the arrows back into coincidence,

and read the size diierence on his scale. By ap- 3o plyinar corrective trial lenses, the arrows can be brought to coincidence, the defect being indicated by the trial correction.

Fig. 53 illustrates a modification of the above test. Instead o1 a fusion object projected with unpolarized light, the examiner uses a fusion object combined ci two similar patterns projected in superimposition from two adjustable lanterns, with l and r light, respectively.. At A of Fig. 53 the initial appearance of this pattern to the` euaminer, to a person not having a size difference, and to a person having a size diiference (again right eye ocular image larger) are indicated. Ii now the fusion squares are moved apart in vertical direction (B o1' Fig. 53). the arrows will 4. move apart for the person with unimpaired vision, while the aniseikonic patient will see them y in coincidence, it the distance ci the two fusion patterns corresponds to his size defect. Upon moving the fusion pattern still further apart, short of breaking fusion (C of Fig. 53), the isei ironic person will see the arrows still further apart, whereas-the anisekonic patient observes a discrepancy opposite to that illustrated at A.

With this set up, the ocular image discrepancy can be measured by means oi' the actual distance or the two components of the fusion pattern when the arrows coincide; this distance will correspond to the apparent distance oi the arrows when the fusion pattern components are in exact super- 50 imposition.

By using, in addition to the test pattern indicated ln Fig. 53, a .fusion object consisting of a simple pattern (for example Fig. 31) projected with unpolarlzed light, the test illustrated in 65 Fig. 54 can be made. Assuming that the patient does not have a size diiierence in the meridianv in question, position A of Fig. 54 corresponds to the rst two squaresoi B in Fig. 53. If the additional fusion pattern is now projected into the vicinity of the arrows, it will be seen double asA indicated at B of Fig. 54.` Gradually, however, central fusion becomes stronger than peripheral fusion and the appearance changes, as shownA at 75 C. `In this manner, the relation of central` and peripheral power to fuse can be investigated.

Referring to Fig. 55, a test will now be described for determining whether or not a patient has in a given meridian a symmetric or an asymmetric size defect, the latter type of aniseikonia being for example described incopending application Serial No. 750,162, filed'A October 26, 1934. For the purpose of this explanation it'will be presumed that vin the case of both symmetric and asymmetric aniseikonia the upper half of the ocular image for the right eye is larger than for the lei't eye whereas, for asymmetric aniseikonia, the lower half of the right eye ocular image is smaller. A fusion object is again applied as previously described, and steps A to E of Fig. 55 will now be understood without further explanation.

A second fusion object, for example likewise projected with two lanterns, is then introduced Afrom the opposite margin of the visual field, which will have to be adjusted as indicated at F and G o! Fig. 55 in order to bring the arrows to coincldence. Ii the aniseikonia is symmetric, coincidence oi' the arrows is obtained by adjusting the 25 fusion object components symmetrically, whereas an asymmetric defect requires asymmetric adjustment; both types are indicated at F and G, respectively. oi' Fig. 55.

lt will be noted that the last mentioned test may require seven projectors. Some of these, tor example one for one arrow and one or two for a component oi the two fusion objects, may be hand lanterns (PM of Fig. 1) permitting the patient to adjust the test pattern. Of course, similar tests can be made for any visional meridian by appropriately arranging the slides.

Stereopsis is preferably checked by means oi a pair or slides according to F1324, the individual slides projecting l and r light, and the eyes being equipped With l and r polarizing screens, respectively. There are cases where fusion is present whereas the patient does not have stereoptric vision. lin such cases, the patient sees the circles and the point in one and the same plane whereas, with stereopsis unimpaired, the pattern appears as indicated'in Fig. it will be ,understood that dots itl and liti are projected with l and r polarized light, respectively, and square 555 with 'unpolarized or Zr light. 'l'his is a test as to the quality of Stereopsis, whereas the well known Keystone pattern projected with slides, Fig. 25, permits quantitatiye tests, the various patterns appearing in ten different planes ii normal steropsis is present.

The test described with reference to Fig. 22

.permits the determination of stereoscopic amplil'-Ihe well known horoptric tests (compare for example The Journal of theV Optical Society ofv America, vol. 22, page 538) can be carried out by means of a pair of slides according to Fig. 2'?. One slide being projected with Z and the other with r light, this pattern replaces the known horoptrie device. with adjustable wires. It is used without fusion pattern, the eyes being. 

